The present invention relates to a tracer device having a tracer arm which is mounted in an axial guide and is movable back and forth in the x direction while measuring the path, and a tracer head which is mounted at the free end area of the tracer arm, is in contact with the surface of a part during a measurement and, during its travel in the x direction, is deflected by the surface contours in a z direction which is perpendicular to the x direction, and having an analyzer device which detects and analyzes the deflections in the z direction as a function of the path in the x direction.
A tracer device, for example, like that in the German catalog of Taylor Hobson, 7/97, pp. 2, 3, may be used for measuring surface structures such as, for example, small radii or the roughness of metal materials in the order of magnitude of a few micrometers. A tracer head which traces the surface by tactile scanning while being deflected in the z direction according to the surface contour, having a suitable (e.g., pointed or rounded) tracer tip, is mounted on a rigid tracer arm which is movable back and forth in an axial direction (x direction) and is mounted pivotably about an axis on the device in the area of the axial guide.
The pivoting movements are converted into electrical signals as a function of the path in the x direction and electronically analyzed to evaluate the traced surface contour. Difficulties may arise in such a tracing when the surface to be traced is located inside a narrow channel of the part, which, in addition, cannot be viewed laterally. For this reason, such tracer devices are used for measuring open, visible surfaces. To expose an internal surface, the part is cut open and thus destroyed.
To non-destructively measure internal surface structures, such as radii on two bore holes running perpendicular into each other, an elastomer impression method may be used, for example.
An object of an exemplary embodiment of the present invention is to provide a tracer device by which particular surface structures can also be easily measured even in narrow bore holes of a part.
The front section of a tracer arm, which is rigid per se, is provided with a tracer leg which forms an articulated link of the tracer head to the tracer arm, a measuring element which detects the deflection in the z direction being arranged on the tracer leg.
Since the tracer arm, which is rigid per se and is rigidly held in the axial guide, is not moved in the z direction over its entire length, and only the tracer leg mounted on it which is relatively short is moved, the tracer arm with its tracer leg can also be inserted deep into narrow channels of a part in order to take surface measurements there. For example, roundings in the area of bore holes running transversely to one another having rounding radii in the range of a few micrometers can be traced without difficulty. It is believed that the danger of the tracer head becoming hooked on the surface is also considerably diminished, since the long and rigid tracer arm is no longer deflected.
The tracer leg is fixedly attached to the tracer arm and is designed to be flexible, the term xe2x80x9cfixedlyxe2x80x9d meaning that the tracer leg forms a fixed articulation (as opposed to a loose articulation), so structures in the range of less than 1 xcexcm can still be traced and the danger of the tracer head becoming hooked is further substantially diminished. The tracer leg can also be mounted replaceably on the tracer arm to enable different tracer heads to be used, for example.
Different detecting devices for the deflection in the z direction may be obtained since the measuring element is an expansion measuring strip unit, an optical deflection element, or a piezoelectric, inductive, or capacitive sensor.
It is believed to be advantageous if the expansion measuring strip unit has two paired expansion measuring strips to compensate for temperature errors.
Another exemplary embodiment that is different from the tracer leg which is fixedly mounted on the tracer arm has a tracer leg connected to the tracer arm via an articulated shaft as a rocker. A xe2x80x9csimplexe2x80x9d design may be implemented by connecting the rocker to an optical deflection element or by providing it with an inductive or capacitive sensor to detect the pivoting of the rocker.
A xe2x80x9csimplexe2x80x9d optical measuring sensor, which may be easy to apply under the given circumstances, is obtained by the fact that the optical deflection element is part of an optical arrangement which in turn has a light source mounted on the tracer arm for emitting a light beam which is supplied to the optical deflection element, a waveguide device, and a position-sensitive optical receiver which detects the beam reflected by the optical deflection element. It is believed that assembly and adjustment, as well as measurement in a narrow channel, may be better since the light source and the optical receiver, as well as an optical unit connected upstream from the optical receiver, are arranged on a section of the tracer arm which faces the axial guide.
Adjustment of the tracer device and handling during measurement are substantially simplified since the axial guide can be attached to the part using an adapter that is adapted to an insertion opening of a part to be traced. With these measures, it is believed that an expensive test bench having attaching and adjusting devices is no longer required, since the tracer device is precisely associated with the part via the adapter, and the point of measurement is always precisely established when measuring different parts of the same type and can be easily moved into position, even automatically, without having to visually check the position of the measuring head using simple programming in particular. It is believed that the danger of destroying the measuring head by accidentally hitting an internal wall of the part may also be substantially reduced.
For easily positioning the device with respect to different measuring points within the part, the tracer arm is rotatable about its axis automatically and reproducibly using a control device of the axial guide.